Is TRIM better than Native Command Queuing?

Another question from the big bag ‘o search queries: When you’re shopping for an SSD, is TRIM better than Native Command Queuing?

It’s an interesting question, and my first inclination is to say no, because TRIM and NCQ solve two similar but distinctly different problems. But the more I think about it, the more I understand why it’s possible to confuse the two.

TRIM handles performance degradation caused by repeated deleting of files. I’m oversimplifying the issue here, but generally speaking, writing over existing data is slower than writing over unused space, so TRIM addresses that issue, by giving the operating system a way to communicate with the SSD about file usage, and that allows the SSD to juggle free space to avoid as many rewrites as possible. This provides speed improvements, and it also extends the life of the drive. The catch is that your drive has to have the capability, and your operating system has to be written with TRIM in mind. Windows 7 supports TRIM; Windows XP does not.

NCQ allows SSDs and hard drives to work more intelligently. As you’re using a computer, the operating system will ask the drive to do a lot of things, and the order isn’t always optimal. NCQ allows the drive to rearrange the requests in a more intelligent fashion. Let’s say the computer asks for four reads and four writes. Writes are generally slower than reads. If the reads aren’t dependent on the writes, the drive can do the reads, then do the writes while the computer is processing the data the drive just read.

The difference in performance is noticeable, and it improves the performance of everything a drive does, not just writes.

The best way to ensure you have both TRIM and NCQ enabled is to have AHCI enabled in the BIOS, run an AHCI-aware operating system–anything newer than Windows 7 qualifies–and install fresh to the SSD.

Typically, if a drive does one, it will do the other. If I had to say one was better or more important than the other, I’d have to give the slight edge to TRIM, since it lengthens the drive’s life expectancy. But given the choice between the most advanced mechanical hard drive in the world and a basic SSD with neither, I’d still take the basic SSD.